Mass gatherings(MGs) are crowded events that attract millions of people to exceed the capacity of routine health and public safety measures. WHO defines MGs as 'events attended by a sufficient number of people to strain the planning and response resources of a community, state or nation. For effective public health management, the role of psycho-social factors in managing the health-related behaviour of attendees needs to be investigated. Previous research suggests that health risk perception plays a crucial role in shaping individuals' responses to hygiene, sanitation and crowd dynamics. These responses shape health-related behaviour in special reference to infectious diseases. This paper explored the general health-related behaviour among the attendees of one of India's largest religious mass gatherings held post-COVID outbreak, the Kumbh Mela 2021. It examined the role of shared identity among attendees and its impact on health-related behaviour through perceived health risk perception within the special context of Kumbh Mela. The study adopted a mixed-methods approach. 30+ on-spot in-depth interviews were conducted with health professionals who were appointed at the Kumbh Mela to understand their experience of dealing with patients. A survey on a sample of 400 attendees was conducted to assess social determinants of health risk perception, such as shared identity, disgust sensitivity, positive experience and perceived health and wellbeing. Thematic analysis of interviews and a multivariate analysis of the survey reflect that shared social identification leads to better-perceived health and well-being through undermining health risk perceptions in mass gatherings. These findings have important implications for understanding how crowd dynamics may aggravate health risk behaviours in mass gatherings. The present research should contribute to efforts to understand the nature and scope of social identity processes in aggravating and mitigating health behaviour in mass gatherings.